Toxin delaying California crab season also inspired horror movie

Santa Cruz Sentinel staff photographer
The Sentinel’s front-page photo on August 18, 1961: “Sheriff’s Deputy Ed Cunningham inspects the damage to his prowl car roof early this morning when a sooty shearwater seabird seeking light crashed into the car spotlight. Thousands were stranded in the Capitola/Pleasure Point area.”

CAPITOLA >> In August 1961, Capitola residents awoke to a scene that seemed straight out of a horror movie. Hordes of seabirds were dive-bombing their homes, crashing into cars and spewing half-digested anchovies onto lawns.

Famed film director Alfred Hitchcock even used the incident as research material for his then-in-progress movie “The Birds,” in which flocks of deranged birds inexplicably attack a coastal town.

Just as the unexplainable avian attacks in “The Birds” have terrified movie buffs for more than half a century, the 1961 frenzy puzzled scientists for decades. They now believe the culprit was domoic acid — the same neurotoxin that has delayed this year’s Dungeness crab season in California.

The toxin is produced by certain types of algae blooms. In humans, it can cause vomiting, diarrhea and even short-term memory loss. Marine animals become disoriented or have seizures. Now, public health agencies periodically test for its presence and restrict fishing when it’s found in high doses, as they did recently in California. But in 1961, it hadn’t even been identified.

So when the Santa Cruz Sentinel reported on Aug. 18, 1961, that “dead and stunned seabirds littered the streets and roads,” experts could only blame the fog. When Hitchcock, who owned a house in Scotts Valley, heard about the mysterious incident, he called the Sentinel asking for more information.

Domoic acid was first identified as a shellfish toxin in 1987, after three people died and hundreds were sickened by mussels from Prince Edward Island. Shortly afterward, it was implicated in a 1991 seabird die-off in Monterey Bay, according to Michael Quilliam. Quilliam, a researcher at the National Research Council in Halifax, Nova Scotia, was involved in both projects.

Still, there wasn’t conclusive evidence for the 1961 incident. Lacking actual birds from 50 years prior, Sibel Bargu, a researcher at Louisiana State University, instead analyzed historical samples of zooplankton.

Filter-feeding zooplankton are “like a trash can,” she said. They eat algae and accumulate toxins that are then passed on to other animals higher up the food chain.

The zooplankton had high levels of domoic acid-producing algae in their guts, leading Bargu and her colleagues to conclude in a 2012 paper that a toxic algae bloom had indeed occurred in the area at the time of the invasion.